Large sized fuel burners used in commercial and industrial buildings, as well as, in process control have for many years utilized progammers that operate primarily by using motor driven cam operated switches and electromagnetic relays to provide the necessary logic and sequence for safe burner operation. Most of the programmers on the market were designed for the ignition of either gas burners, or of gas burners which subsequently were augmented by the addition of fuel oil. Most burners which operate directly on oil utilize spark ignition of the fuel oil substantially immediately upon the energization of the burner. Since the advent of the fuel shortage, and due to changes in general economic considerations in fuel burners, the oil burner has become more important. Large oil burners have substantially different characteristics than gas burners, and require a different sequence for their initiation if safety is to be properly provided for. Most gas burners utilize a prepurge period to clear the combustion chamber of unburned products before the initiation of the burner cycle. This is not necessarily true of oil burners, and the use of a prepurge in a oil burner can create an unsafe condition by oil pressure forcing oil into the combustion chamber past a leaky oil valve and result in the accumulation of a dangerous amount of fuel in the combustion chamber.
The special needs of oil burners, versus gas burners, is becoming more and more apparent and the provision of special equipment for oil burners for safe operation has become necessary. A programmed sequence for safe start-up of a gas burner may not be a safe sequence for start-up of an oil burner. The need of a special sequence for oil burners has thus become apparent.